#app4> .circle{
    border: 1px solid red;
    width: 100px;
    height: 100px;
    margin: 10px 0 0 10px;
    border-radius: 50%;
    transition: transform 1s;

}
@keyframes change {
    0%{
        width: 120px;
        height: 120px;
        margin: 10px 0 0 10px;
        background: red;
    }
    100%{background: red;}
}
#app4> .circle.active{
    animation: change 1s infinite alternate linear;
}